www.ssontech.com

[gallion311]

Hey whats up guys.

Interesting one for you...I've only used Syntheyes for a few different shots and up until this point is always produced an accurate object track, so I'm just not sure about the next steps and how to manually correct the issues.

So basically I'm manually tracking a set of markers on my arm, with the hopes of inserting some robotic/electronic components into my arm.

So the track seems spot on when I preview it in the Syntheyes Perpsective cam. The problem is that it's totally misaligned, it's just a perspective/camera trick that makes it seem like it's accurate in Syntheyes. Upon bringing the track into 3dsMax it's evident how off the object orientation is, like Syntheyes just guessed wrong.

I know this is a tough one to diagnose without seeing it in action, so here's a quick page I put together that includes a ton of resources (the footage, the trackers in 3dsMax, a test render from Max)

http://www.ryangallion.com/armtrack.php

The clip that will best showcase the issue is the one we're I'm moving around in the 3dsMax viewport. From the camera it looks great, but when I orbit around a bit you can see how off the tracking points are...orientation-wise.

Any tips or tricks would be greatly appreciated. I imagine what I need to do is grab 2 or more tracks and give Syntheyes a hint regarding how they are supposed to be aligned?

[The Happy Friar]

I'll say that it's pretty much a 2D flat surface & it can't be tracked properly. I'd suggest either tracking the finger movements too (a good idea) for reference, move your arm around more to get a good track & then do your motions, have someone take pictures from ~5 angles with a camera (or take stills from various angles on a recording) & use that as a reference track.

[The Happy Friar]

Think I got it for ya. I did an automatic object track (with a garbage matt) on it & cleaned up/fixed the trackers manually. I set up a coordinate system so I could see it easier. I exported & used Blender to add an object.

Here's the video I made:
http://www.sterlingshield.net/home/steve/syntheyes/arm test.wmv

Here's the sni file:
http://www.sterlingshield.net/home/steve/syntheyes/arm_test.sni

[gallion311]

Thanks Friar, much appreciated.

That's an interesting point about the 2D aspect of the footage, with such a lack in parallax I guess it's just difficult for Syntheyes to figure it out?

Track looks better, but I am curious about the "cleaned up/fixed the trackers manually" part.

So what exactly does that entail? Are you going in and manually adding coordinate references? Or does that only work with Camera tracking?

The interesting aspect is that this is my second, more polished attempt at this type of shot. The first one I did was almost perfect, I just wanted to reshoot with a few more bells and whistles in the background...

Take a look at the first attempt, added to the same page above ^^.

So what is different about that clip? Did I accidentally have more parallax in that shot?

Is it the dots being spread out in a larger surface?

[The Happy Friar]

I'd say the larger surface & almost twisting your arm 90% helped a lot. What you could do is keep the dots in the same spot on your arm for each shoot & use that one good track as a reference and solve the others indirectly.

For manually fixing things I deleted all the trackers I didn't want (basically the ones not in the sni file). Then the ones I DID want I selected each one at a time and played through the file, watching to look for when it turned off, lot the dot for a split second, etc. I fixed those if I could (I could of combined some trackers but deleted them first, I should of used the tracker graph to check things out first. My mistake!)

In my question about my lego tracking Russ told me that you could change the two frames it uses as the initial track too, so I did that once. That helped.

[metalfish]

In the older shot you markers were in a wider area on your arm.. in the new one all trackers are at one place, so there is less depth information.

Perhaps it would be a good idea to move your "moving object" more right before you do your actual shot. Move your arm towards the camera, turn it in all directions, so the tracker has more information to estimate the positions in 3d Space. you can cut that away later, its just to improve tracking...And add some more markers on your arm in a wider area...

[ShadowMaker SdR]

The flexing of your muscles in the first shot doesn't help either. That makes the dots move in non-rigid ways. Making a track much more difficult. If you had taped a thin piece of wood or plastic to your arm that would've helped the track as well.